Method of securing diamond by brazing

ABSTRACT

Method of securing diamond by means of brazing with a brazing filler consisting of an alloy of aluminum and silicon which contains from 8 to 18% by weight of silicon.

United States Patent Knippenberg et al.

[4 1 v July 25, 1972 METHOD OF SECURING DIAMOND BY BRAZING [72]Inventors: Wilhelmus Franciscus Knippenberg; Gerrit Verspui, both ofEmmasingel, Eindhoven, Netherlands I [73] Assignee: U.S. PhilipsCorporation, New York, NY.

[22] Filed: June 29, 1970 21 Appl. No.: 50,851

[30] Foreign Application Priority Data July 2, 1969 Netherlands ..e9101I5 [52] US. Cl ..29/473.l, 29/504, 287/l 89.365

[51] Int. Cl ..B23k 31/02 [58] Field of Search ..29/473. 1 504; 287/]89.365

[56] References Cited UNITED STATES PATENTS 2,820,534 1/1958 Hume .1...29/504 X 3,09 l .029 5/1963 Davis et al. ..29/504 X 3,l92,620 7/1965Huizing et al. ....287/l 89.365 X 3,377,696 4/l968 Darrow....287/l89.365 X 3,39l,446 7/1968 Buttle 29/4731 X 3,477,l l8 ll/l969Terrill 29/4731 X FOREIGN PATENTS OR APPLICATIONS 240,687 ll/l959Australia ..29/473.]

Primary Examiner-John F. Campbell Assixlanl Examiner-Ronald J. ShoreAlmrney--Frank R. Trifari [57] ABSTRACT Method of securing diamond bymeans of brazing with a brazing filler consisting of an alloy ofaluminum and silicon which contains from 8 to 18% by weight of silicon.

4 Claims, 3 Drawing Figures PATENTED JUL25 I972 2 1 I in y///// Fig.3

INVENTORS PPENBERG LHELMUS F.

RIT VERS METHOD OF SECURING DIAMOND BY BRAZING The invention relates toa method of securing diamond by means of a brazing.

It is known that a mechanically very strong securement of diamond, inexample for the manufacture of tools, may be effected with the aid of abrazing filler of titanium on the basis of silver and copper. In thatcase the wetting of the diamond surface is in fact effected by titaniumor a compound of titanium and one of the other metals produced at thesoldering temperature.

A drawback of the use of titanium is that it readily forms oxide ornitride; titanium oxide and titanium nitride do not contribute to thewetting of the diamond surface. In this known method soldering orbrazing must therefore be performed in a vacuum or in an inertatmosphere. According to a further known method brazing is performedwith an alloy of gold comprising at least 1 percent by weight andpreferably approximately 5 percent by weight of tantalum and/or niobium.These alloys are less reactive to oxygen and nitrogen, so that brazingin a lower vacuum or in a less pure rare gas atmosphere may be performedwithout the disadvantages as in the case when using the previouslymentioned titanium-containing copper-silver alloys.

A drawback of the two known methods described is that brazing is to beperformed at a temperature of approximately l,000C when using thesilver-copper alloys containing titanium and between 1,200 and l,400Cwhen using alloys of gold containingtantalum and/or niobium because thealloys used havehigh melting points.

An objectof the present invention is to obtain a satisfactorily adherentjoint to diamond for which brazing is performed at temperatures whichare lower than those mentioned above.

The present invention relates to a method of securing diamond by meansof brazing in an inert atmosphere, characterized in that brazing isperformed using an alloy of aluminum and silicon which contains from 8to 18 percent by weight of silicon.

Alloys containing from 10 to 12 percent by weight of silicon arepreferably used, because these have the lowest melting points.

The approximately eutectic alloys of aluminum and silicon which are usedin the present invention melt at temperatures of from 570 to 670C.Brazing may be performed at approximately 700C with the aid of thesealloys.

A further advantage of the method according to the invention is thatbrazing may be performed under less critical circumstances regarding thebrazing milieu. To prevent oxida tion of the alloys and attack of thediamond, the brazing operations (as in the previously known methods) areperformed in a vacuum or in a protective gas as for example, nitrogen,hydrogen, or a rare gas. The presence of some oxygen is less disturbingthan in the known methods.

An additional advantage is that the aluminum-silicon alloys are soductile that they can satisfactorily be processed to form wire and foil.These material shapes render the performance of the soldering operationsimple.

The alloys used herein are already known as brazing materials. However,it is not known that a particularly adherent joint to diamond may beestablished with these alloys.

Furthermore, it is advantageous in the present invention to useapproximately eutectic aluminum-silicon alloys to which a small quantityof an element is added which may be active as an anti-oxidant duringsoldering, while the oxide formed therefrom has a wetting activity, forexample, lithium.

The alloys used in the present invention make it possible to securediamonds very tightly to materials having coefficients ofexpansion whichare different from that of diamond, such as quartz, silicon carbide,graphite, ceramic material and metals,

for example, tungsten, molybdenum, nickel and steel. The fact that goodsecurement is obtained, which is in-sensitive to fluctuations intemperature, may relate to the ductility of the alloys.

It should be noted that aluminum alloys have already been Proposed asbinders for diamond grains in rindin tools and, or example, alloys ofaluminum containing mm 5 to 70 per- EXAMPLE 1 As is diagrammaticallyshown in a cross-section in FIG. 1 of the accompanying drawing, adiamond cutting tool was manufactured by fixing a diamond plate 1 of 5 X2 X 1 mm on a sur' face 3 of a steel holder 2 by means of the brazinglayer 4.

To this end a piece of foil (thickness 20 um) comprisingaluminum-silicon alloy containing 12 percent by weight of silicon waslaid on the surface 3 of the steel holder 2 and the diamond was placedthereon in such a manner that it partially extended sideways from theholder.

While the diamond plate I was mechanically fixed relative to the steelholder 2, for example, with the aid of a ceramic pin (not shown in theFigure) the assembly was subsequently heated in a furnace at 700C for 1minute in an atmosphere of technical argon.

EXAMPLE 2 A diamond grammophone stylus was secured to a molybdenumsupport as follows (FIG. 2).

A rod-shaped diamond 11 (length 0.5 mm, diameter approximately 0.2 mm)was clamped with the aid of a spiral 12 of molybdenum wire to one end ofa molybdenum rod 13 (diameter 0.8 mm). Subsequently, this end wasimmersed for 10 seconds in an aluminum-silicon alloy 14 containing 1 lpercent by weight of silicon which was kept molten in a carbon crucible15 in a nitrogen atmosphere at 750C. The alloy then flowedsatisfactorily onto the diamond and the molybdenum and produced a tightsecurement. Finally, the diamond thus secured was ground.

EXAMPLE 3 Diamond bearings for precision instruments, for example,watches (FIG. 3). Diamond bearings 21 having a conical bore were brazedon an assembly plate 22 of stainless steel with the aid of analuminum-silicon alloy 23 (containing 13 percent by weight of silicon).To this end the bearings were mechanically fixed in predetermined areaswith the interposition of foil of this alloy and the assembly was heatedfor 30 seconds in a nitrogen atmosphere at 700C.

We claim:

I. A method of securing diamond to a support comprising brazing thediamond to the support in an inert atmosphere using an alloy consistingessentially of aluminum and silicon containing from 8 to l8 percent byweight of silicon.

2. The method of claim I wherein said brazing is performed using analloy consisting essentially of aluminum and silicon containing from 10to 12 percent by weight of silicon.

3. The method of claim 1 wherein said brazing is performed using analloy containing a deoxidant the oxide of which has a wetting action.

4. The method of claim 3 wherein said deoxidant is lithium.

2. The method of claim 1 wherein said brazing is performed using analloy consisting essentially of aluminum and silicon containing from 10to 12 percent by weight of silicon.
 3. The method of claim 1 whereinsaid brazing is performed using an alloy containing a deoxidant theoxide of which has a wetting action.
 4. The method of claim 3 whereinsaid deoxidant is lithium.